全文获取类型
收费全文 | 387篇 |
免费 | 46篇 |
国内免费 | 166篇 |
出版年
2024年 | 6篇 |
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 23篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 22篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 23篇 |
2013年 | 24篇 |
2012年 | 39篇 |
2011年 | 49篇 |
2010年 | 32篇 |
2009年 | 27篇 |
2008年 | 38篇 |
2007年 | 23篇 |
2006年 | 33篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 12篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有599条查询结果,搜索用时 46 毫秒
1.
K. Takezawa B. Moorthy M. L. Mandel J. C. Garancis J. G. Ghazarian 《Histochemistry and cell biology》1990,95(1):37-42
Summary Chick 25-hydroxyvitamin D3-1-hydroxylase, a cytochrome P-450 monooxygenase with a molecular weight of 57 kDa, can be isolated as described by Mandel et al. (1990b). Under normal physiological circumstances, it occurs exclusively in kidney mitochondria. An isozyme of the 1-hydroxylase, known as the 24-hydroxylase, which uses the same substrate to yield an isomeric product, is also a cytochrome P-450 monooxygenase, has a molecular weight of 55 kDa, and likewise occurs in kidney mitochondria. The amino-terminal sequences of the first 10 residues of the two isozymes are 100% homologous. Monoclonal antibodies of the IgM class raised against the 1-hydroxylase, which quantitatively discriminate against other P-450 cytochromes of mitochondrial or microsomal origin, recognize and interact with the 24-hydroxylase as an antigen. In the present study we show that the intestine, which is the only non-renal tissue with demonstrable 24-hydroxylase activity, gives a positive peroxidase-antiperoxidase immunohistochemical reaction using the monoclonal antibodies against the 1-hydroxylase. The reactions revealed that the antigen in the kidney is restricted to the cortical proximal tubular cells while in the intestine, the antigen is localized in the enterocytes of the villi. In kidney medullary or intestinal crypt cells, or in liver, heart and lung tissues where 1-hydroxylase or 24-hydroxylase activity could not be detected using cell or tissue homogenates, the immunohistochemical reactions were also negative. Since it has been reported that chick embryonic intestine possesses 1-hydroxylase activity that is absent in the mature intestine, our results would suggest that the mature intestinal 24-hydroxylase represents a modified 1-hydroxylase as a consequence of developmentally imposed requirements regulating calcium homeostatic activity in this tissue. The difference in the molecular weights of the two enzymes would indicate either genomic processing prior to the translation of their respective mRNAs, or a post-translational processing of the larger 1-hydroxylase to the smaller 24-hydroxylase.
The abbreviations used are: 25-OH-D3, 25-hydroxyvitamin D3; 1,25-(OH)2D3, 1,25-dihydroxyvitamin D3; 24,25-(OH)2D3, 24,25-dihydroxyvitamin D3, NADP, nicotinamide adenine dinucleotide phosphate 相似文献
2.
司光伟 《生物化学与生物物理进展》2023,50(6):1243-1243
Acetylcholine, the first identified neurotransmitter, plays crucial roles in various brain functions. One well-known case is its involvement as an activating neurotransmitter in the regulation of locomotion. However, its inhibitory regulatory role, particularly in locomotion, remains poorly understood. In a study conducted by Polat et al., the authors investigated the inhibitory role of acetylcholine in locomotion in C. elegans. In this organism, the acetylcholine-gated chloride channel receptor consists of four subunits. The authors thoroughly examined the loss-of-function of each subunit in movement regulation. Interestingly, the mutant worms were still capable of performing various movements such as forward, backward crawling, and turning, suggesting that the overall movement was not significantly affected. However, quantitative behavior analysis revealed subtle yet significant differences in the timing and postures of the movement in these mutants. Furthermore, the authors employed optogenetics to stimulate a specific neuron involved in backward crawling and demonstrated that the loss-of-function of the receptors in individual neurons affects the transitioning between locomotion modes.
This work provides evidence for the inhibitory regulatory role of acetylcholine in locomotion. The loss-of-function of acetylcholine-gated chloride channel receptors likely disrupts the balance of neuronal and circuit physiology, thereby affecting the regulation of locomotion. Moreover, this study highlights the powerful role of quantitative behavior analysis in discovering and understanding more sophisticated functions of neural circuits. 相似文献
3.
Y. Tamura Y. Ono T. Suzuki K. Suzuki Y. Takezawa T. Mashimo Y. Fukabori H. Yuasa K. Imai H. Yamanaka K. Suzuki 《Histochemistry and cell biology》1997,108(6):505-512
It is generally accepted that early human prostate cancers reveal higher androgen dependency than do advanced ones. In the
present study, we examined whether the animal model of prostate cancer has already lost androgen dependency at the early stages
of carcinogenesis. At experimental week 46, androgen deprivation was induced in rats and the incidences of atypical hyperplasia
and cancer were examined in the ventral, dorsolateral prostate, coagulating glands, and seminal vesicles. Androgen deprivation
significantly lowered the incidence of atypical hyperplasia in all four organs. As for the incidence of cancer, no significant
differences were observed in the coagulating glands and seminal vesicles. Regarding atypical hyperplasia, androgen deprivation
significantly decreased the proliferative cell nuclear antigen labeling index in the coagulating gland and seminal vesicles.
The presence of cancer was also decreased in the coagulating gland but not in the seminal vesicles. With control group specimens,
more intense staining of androgen receptor was observed in atypical hyperplasias than in cancers. Compared with the atypical
hyperplasias, the cancers revealed low androgen dependency at the early stages of carcinogenesis. The cancers in the seminal
vesicles also revealed higher androgen independency than did those in the coagulating gland.
Accepted: 6 May 1997 相似文献
4.
栓孔菌属漆酶高产菌株的初步筛选及其产酶条件的优化 总被引:4,自引:1,他引:3
利用显色反应对栓孔菌属(Trametes)进行了漆酶高产菌株的筛选,并对目标菌株的产酶条件进行了优化,在添加愈创木酚的固体培养基中,通过显色反应初步筛选出漆酶高产菌株东方栓孔菌Trametes orientalis Cui 6300;进一步通过单因子分析、正交试验和ABTS法确定了菌株Cui 6300的最适产酶条件:麦芽糖15 g/L,蛋白胨3 g/L,pH 4.8,Cu2+2.0 mmol/L,培养温度28°C,接种饼直径1.5 cm,此时酶活最高可达19.923 U/mL;同时探索了Cu2+浓度及添加时间对其菌丝生物量和漆酶活力的影响。研究表明,Cu2+最适添加浓度为2.0 mmol/L,添加时间为接种后第3天。 相似文献
5.
6.
为建立龙珠果(Passiflora foetida)的快繁再生体系,以实生苗茎段为外植体,研究了植物生长调节剂对丛生芽诱导、壮苗生根的影响,同时对组培苗的耐盐性进行研究.结果表明,MS+6-BA 0.5 mg/L+NAA 0.05 mg/L培养基有利于诱导丛生芽并促进芽的生长;MS+6-BA 3.0 mg/L+NAA ... 相似文献
7.
为了解益智(Alpinia oxyphylla)多糖生物合成途径关键酶功能,对其茎、叶、果实中的多糖含量及其单糖组成进行了研究,并采用Real-Time qPCR分析了益智多糖生物合成关键酶基因的表达模式。结果表明,益智多糖含量依次为果实 > 叶 > 茎,主要由葡萄糖、木糖、甘露糖、半乳糖和阿拉伯糖组成;利用益智转录组数据共获得47 690条unigenes,其中31 892条在NR、Swiss-Prot、KEGG、COG、KOG、GO和Pfam数据库获得注释,其中208个unigenes参与益智多糖的生物合成,涉及15个酶。表达分析表明,所筛选的18个基因在茎、叶、果实中均有表达,14个基因在果实中的表达量最高,以糖基转移酶基因和UDP-葡萄糖焦磷酸化酶基因的表达量最高,且其表达模式与不同组织中葡萄糖含量的变化一致。 相似文献
8.
9.
10.
中亚热带森林转换对土壤磷积累的影响 总被引:3,自引:0,他引:3
磷是植物生长的必需元素之一,是维持亚热带森林生态系统生产力的关键因子。研究森林转换后土壤因素对磷素的影响,对生态系统的稳定和森林经营具有重要意义。选取由亚热带常绿阔叶林转换而成的米槠次生林(SF)、米槠人促林(AR)和杉木人工林(CF)为研究对象,测定了土壤理化性质、铁铝氧化物、各形态磷含量以及酸性磷酸酶活性,旨在探究土壤磷对森林转换的响应和驱动土壤磷变化的影响因子。结果显示:米槠人促林土壤的全磷、有机磷和微生物生物量磷显著高于米槠次生林和杉木人工林;冗余分析(RDA)发现,土壤含水量、总氮和无定型铁是影响淋溶层土壤磷的主要因子,而在淀积层,则是酸性磷酸酶、游离型铁和总氮起主要作用;土壤生物化学属性和微生物特性都会影响着不同形态土壤P的积累,其中土壤中的水分和酸性磷酸酶活性是调控土壤磷的关键因子。研究表明,中亚热带地区天然林转换为人促更新林更有利于森林土壤磷的储存和供应,有助于维持本区域森林生态系统的稳定。 相似文献